Display and Input Device and Image Forming Apparatus Including the Same

1. A display and input device comprising: a display section configured to display thereon a screen image including one or more operation element images each operable to cause switching of the screen image and a non-operable region in which no operation element image is present; a touch screen section configured to detect a touch position on the screen image; a control section configured to detect a set of touch position coordinates of the touch position based on output from the touch screen section, compare the detected touch position coordinates with image data of the screen image displayed on the display section to determine that when a display position of any of the operation element images overlaps the detected touch position coordinates, the overlapping operation element image is operated, and control the display section to switch the screen image according to the operation element image operated; and a storage section configured to store therein detection coordinate data showing coordinate values associated with possible output values of the touch screen section and at least a predetermined number of sets of touch position coordinates detected in succession including a set of touch position coordinates most recently detected, wherein the display and input device uses a normal mode for selecting any of the one or more operation element images and a calibration mode for correcting the detection coordinate data, on detecting a touch operation in the non-operable region the predetermined number of times in succession, the control section switches modes from the normal mode to the calibration mode, additionally displays on the display section a target point image for calibrating coordinate detection other than the one or more operation element images in the calibration mode, determines an amount of deviation between a set of touch position coordinates detected after display of the target point image and a set of display coordinates of the target point image, and calibrates the detection coordinate data such that each set of touch position coordinates subsequently detected is corrected in accordance with the amount of deviation.

2. The display and input device according to claim 1 , wherein when the predetermined number of sets of touch position coordinates detected in succession all fall within the non-operable region and a difference among the predetermined number of sets of touch position coordinates is within a predetermined permissible range, the control section determines, as the set of display coordinates, one of the predetermined number of sets of touch position coordinates detected in succession or a set of average coordinates of the predetermined number of sets of touch position coordinates detected in succession and displays the target point image at a position overlapping the determined set of display coordinates.

3. The display and input device according to claim 2 , wherein when the determined set of display coordinates falls outside a display region of the display section, the control section corrects either or both of a vertical axis coordinate and a horizontal axis coordinate of the determined set of display coordinates through a predetermined procedure to specify such a position that the target point image is displayed in the display region of the display section and displays the target point image at the set of display coordinates as corrected.

4. The display and input device according to claim 3 , wherein when the vertical axis coordinate of the determined set of display coordinates falls outside the display region of the display section, the control section corrects the vertical axis coordinate to specify such a position that the target point image is displayed on a horizontal edge of the display region, the horizontal edge being a closer one of two horizontal edges to the vertical axis coordinate before the correction, and when the horizontal axis coordinate of the set of display coordinates falls outside the display region of the display section, the control section corrects the horizontal axis coordinate to specify such a position that the target point image is displayed on a vertical edge of the display region, the vertical edge being a closer one of two vertical edges to the horizontal axis coordinate before the correction.

5. The display and input device according to claim 3 , wherein when displaying the target point image at the set of display coordinates as corrected, the control section additionally displays on the display section a message indicating that a calibration process needs to be performed a plurality of times, after performing a first calibration process of the detection coordinate data based on a set of touch position coordinates detected with respect to the target point image displayed at the set of display coordinates as corrected, the control section displays the target point image at a predetermined set of display coordinates and performs an additional calibration process one or more times, and the additional calibration process is performed based on a set of touch position coordinates detected after display of the target point image at the predetermined set of display coordinates.

6. An image forming apparatus comprising the display and input device according to claim 1 .

7. The display and input device according to claim 1 , wherein when displaying the target point image on the display section in the calibration mode, the control section displays on the display section a message indicating that a calibration process will be performed to correct the detection coordinate data.

8. The display and input device according to claim 1 , wherein the predetermined number of times the touch operation is detected is a plural number of times.